Presently, the disposable sterile syringes widely used in hospitals and medical organizations domestically and abroad don't possess entirely the characteristic of being disposable in respect of their using performance due to their configuration, so they can be reused after some reset. For example, most of known self-destructive syringes are designed generally to destruct the sealing of injecting pistons after the medical liquid is fully expelled so that they can be used only once. However, if the injecting piston and injecting piston-rod are not advanced to the final position (i.e. some medical liquid is remained) when using the syringe, the piston can not be destructed and can be reused. In order to solve the above-mentioned problem, the China patent application with the application number CN03264428.0 filed on 18th Jun. 2003, the certificate is ZL03264428.0, the applicant is Wuxishiyushou medical-appliance Company and the designers are Fengzhong, Wangjunyi and Feijianguo disclosed a disposable self-destructive syringe comprising ratchet grooves and an anti-return member, wherein said teethed ratchet groove is provided in the entire gap in the injecting piston-rod and said anti-return member is arranged on the rear end of the ratchet grooves, and the ratchet grooves and the anti-return member are arranged together in the cylinder (i.e. the housing) of the syringe. When sucking medical liquid, the injecting piston-rod is pulled backward, but the anti-return prods provided on the anti-return member keeps still due to its pressing against the inwall of the cylinder, thereby the ratchet grooves pass the anti-return member. When stating injecting after sucking medical liquid, the anti-return member will be pushed forward together with the injecting piston-rod for being locked by the ratchet groove, and the piston-rod can not be pulled backward again to suck medical liquid because the anti-return member is continuously pressing against the inwall of the tube, thereby realizing the disposable function. But the said syringe has some clinical limitations. The syringe can not completely expel the air inhaled during sucking medical liquid and even may waste medical liquid for having no structure for expelling air. Furthermore, the syringe can not be used as high dose-precision syringe for injecting bacteria and insulin because of not having taken the remainder of medical liquid into account. In order to overcome the above limitations, the invention provides an improved disposable self-destructive syringe.